Diabetes is a significant problem among blind people and diabetes is a significant cause of blindness. The incidence of blindness increases in older people so that as the life expectancy of diabetic people increases, blindness becomes an increasing problem. In light of these well-known medical facts, there is a need for apparatus to enable blind, visually impared and other people to perform urine glucose tests reliably and without assistance from others.
Chemically impregnated test devices are available for making urine glucose tests. For example, the "Test-Tape" paper of the Eli Lilly Company and the "Uristix" stick of the Ames Company are commercially available test devices. These test devices, when placed in urine, undergo a chemical reaction. The chemical reaction is one in which there is a reduction of an impregnated cooper substance from the cupric to the cuprous state as a function the sugar level in the urine. The reduction causes an attendant development of an orange pigment. The reaction, and hence the sugar level in the urine, is measured as a function of the reflectance (or transmittance) of the test device at a specified time following contact with the urine.
While these test devices can be used by people having normal vision, blind and visually impared people cannot see the pigment change and therefore cannot utilize these test devices without assistance. There is a need, therefore, for an intensity meter which is capable of measuring the intensity of chemically impregnated test materials.
In addition to the specialized need to provide intensity meters capable of use by blind people, a broader need also exists for improved intensity meters which are compact and economical and which are accurate notwithstanding changes of intensity in the light source.